<p>A novel non-prestressed concrete precast base slab incorporating perforated steel ribs and cross-shaped steel shear keys is presented. The flexural performance of the slab was evaluated through full-scale experiments and finite element simulations. The feasibility of support-free construction was also assessed. Two full-scale specimens with different rib cover thicknesses were fabricated and tested under four-point loading. Crack development, load–deflection responses, and concrete strain distributions were recorded. In parallel, a finite element model was developed and validated using the experimental results. A parametric study was then performed to quantify the influence of key parameters on flexural behavior. The simulations showed good agreement with the experiments, and the errors of characteristic values, including cracking load and ultimate load, were within 7%. A reduction in rib cover thickness increased the cracking load by up to 8.7% and the cracking deflection by up to 9.7%. The steel ribs substantially improved slab performance, increasing the ultimate load capacity by 27.19% and the ultimate deflection by 80.69%. To satisfy the criteria for support-free construction, specimen NPS-H2B10 was optimized by adding a top layer slab. The optimized configuration showed that the cracking moment exceeded the moment under the characteristic value of load effect combinations, and the cracking deflection remained well below the deflection limit. These findings provide a reference for support-free construction and structural optimization of non-prestressed precast concrete slabs.</p>